WO2011142027A1 - Process for production of isopropanol, and genetically modified yeast capable of producing isopropanol - Google Patents

Abstract

Isopropanol can be produced with high productivity by employing a fermentation process. Genetically modified yeast is cultured, thereby producing isopropanol in a culture medium with high productivity, wherein the genetically modified yeast has, introduced therein, an acetoacetyl-CoA synthase gene, a group of genes encoding a group of enzymes capable of synthesizing isopropanol from acetoacetyl-CoA (i.e., a group of genes involved in the synthesis of isopropanol).

Description

Isopropanol production method and recombinant yeast having isopropanol production ability

The present invention relates to a method for producing isopropanol using recombinant yeast having isopropanol-producing ability in which a gene group related to isopropanol biosynthesis is incorporated, and the recombinant yeast.

In recent years, there have been calls for the depletion of petroleum resources and the reduction of the amount of carbon dioxide generated at the global level. In the future, oil prices are expected to rise, and the development of alternative materials for oil is required. For example, an attempt to bioconvert biomass, sugar, starch, fats and oils, etc. produced by plants from water and carbon dioxide by solar energy and use it as an alternative material for petroleum has been put into practical use. As an example, technological developments are underway to produce plant-derived polylactic acid and polybutylene succinate as substitutes for plastics using petroleum. In the US, Brazil, etc., ethanol is fermented and produced from sugar, starch, etc., and blended with automobile fuel purified from petroleum.

Further, acetone and isopropanol (synonymous with 2-propanol) are important chemical products as raw materials for industrial solvent resins such as paints and inks. Isopropanol has been conventionally synthesized using petroleum as a raw material, but it is desired to synthesize it from biomass using a fermentation process due to the problems of depletion of oil and reduction of atmospheric CO ₂ . Conventionally, Clostridium acetobutylicum is known to fermentatively produce acetone and isopropanol together with butanol (Non-patent Document 1: Biotechnology, 2nd Edn., Vol1, p285-323, 1993). It is also known that acetone is synthesized by introducing an acetone synthesis gene derived from Clostridium acetobutylicum into E. coli (Non-patent Document 2: Appl. Environ. Microbiol., 73, 1079-1085, 1998, Patent Document 1: US2008 / 293125). Patent Document 2: WO 2009/008377, Patent Document 3: WO 2009/028582).

Furthermore, an example of synthesizing isopropanol using Escherichia coli introduced with isopropanol dehydrogenase gene in addition to the acetone synthesis gene derived from Clostridium acetobutylicum has been reported (Non-patent Document 3: Appl. Environ. Microbiol., 64, 7814). -7818, 2007). However, bacteria such as Escherichia coli are considered to have a low resistance to organic solvents, and several methods are known to solve them. However, in order to produce organic solvents industrially, Resistance is insufficient (Patent Document 4: WO 2007/146377, Patent Document 5: WO 2007/130560, Patent Document 6: WO 2008/073406, Patent Document 7: US 6,156,532). In bacteria such as Escherichia coli, the problem is that the cell membrane is weak against organic solvents, and bacteria are considered unsuitable for organic solvent production. On the other hand, yeasts have high resistance to organic solvents, but no examples of producing organic solvents such as isopropanol and acetone by introducing genes into yeast have been reported.

US 2008/293125 WO 2009/008377 WO 2009/028582 WO 2007/146377 WO 2007/130560 WO 2008/073406 US 6,156,532

Therefore, in view of the above situation, the present invention provides a method for producing isopropanol with excellent productivity by a fermentation process using yeast, and also provides a recombinant yeast excellent in isopropanol production ability. For the purpose.

As a result of intensive studies by the present inventors to achieve the above-described object, a gene group (isopropanol synthesis-related gene group) encoding an acetoacetyl-CoA synthase gene and a group of enzymes that synthesize isopropanol from acetoacetyl-CoA, and As a result of culturing the recombinant yeast introduced with sucrose, it was found that isopropanol was produced at high yield, and the present invention was completed. The present invention includes the following.

(1) culturing a recombinant yeast introduced with an acetoacetyl CoA synthase gene and an isopropanol biosynthesis related gene group related to a metabolic pathway for synthesizing isopropanol from acetoacetyl CoA, and obtaining isopropanol from the culture; A method for producing isopropanol, which is characterized.

(2) The method for producing isopropanol according to (1), wherein the acetoacetyl-CoA synthetase gene encodes an enzyme that catalyzes a reaction for converting acetyl-CoA and malonyl-CoA into acetoacetyl-CoA.

(3) The method for producing isopropanol according to (2), wherein the acetoacetyl CoA synthase gene is a gene derived from a microorganism belonging to the genus Streptomyces (ORFn gene).

(4) The acetoacetyl-CoA synthase gene encodes a protein having the amino acid sequence set forth in SEQ ID NO: 1, or has an amino acid sequence having 80% or more identity with the amino acid sequence of SEQ ID NO: 1, The method for producing isopropanol according to (2), which encodes a protein having a function of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA.

(5) The isopropanol biosynthesis related gene group is a gene selected from the group consisting of an acetoacetyl CoA transferase gene, an acetoacetate decarboxylase gene, and an isopropanol dehydrogenase gene. Of isopropanol.

(6) The recombinant yeast is an isopropanol biosynthesis related gene group into which a non-inherent gene is introduced among acetoacetyl-CoA transferase gene, acetoacetate decarboxylase gene and isopropanol dehydrogenase gene. The method for producing isopropanol as described in (1), which is characterized in that

(7) The method for producing isopropanol according to (5) or (6), wherein the acetoacetyl CoA transferase gene is a ctfA gene and a ctfB gene derived from Clostridiumacetobutylicum.

(8) The method for producing isopropanol according to (5) or (6), wherein the acetoacetic acid decarboxylase gene is an adc gene derived from Clostridiumacetobutylicum.

(9) The method for producing isopropanol according to (5) or (6), wherein the isopropanol dehydrogenase gene is a pdh gene derived from Clostridium beijerinckii.

(10) The method for producing isopropanol according to (1), wherein the acetoacetyl CoA synthase gene and the isopropanol biosynthesis related gene group are introduced into the genome of yeast as a host.

(11) A recombinant yeast introduced with an acetoacetyl CoA synthase gene and an isopropanol biosynthesis related gene group related to a metabolic pathway for synthesizing isopropanol from acetoacetyl CoA.

(12) The recombinant yeast according to (11), wherein the acetoacetyl-CoA synthetase gene encodes an enzyme that catalyzes a reaction for converting acetyl-CoA and malonyl-CoA into acetoacetyl-CoA.

(13) The recombinant yeast according to (12), wherein the acetoacetyl CoA synthase gene is an acetoacetyl CoA synthase gene (ORFn gene) derived from a microorganism belonging to the genus Streptomyces.

(14) The acetoacetyl-CoA synthase gene encodes a protein having the amino acid sequence set forth in SEQ ID NO: 1, or has an amino acid sequence having 80% or more identity with the amino acid sequence of SEQ ID NO: 1, The recombinant yeast according to (12), which encodes a protein having a function of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA.

(15) The isopropanol biosynthesis related gene group is a gene selected from the group consisting of an acetoacetyl CoA transferase gene, an acetoacetate decarboxylase gene, and an isopropanol dehydrogenase gene (11) Recombinant yeast.

(16) The gene group related to isopropanol biosynthesis is a gene into which a non-inherent gene is introduced among acetoacetyl CoA transferase gene, acetoacetate decarboxylase gene and isopropanol dehydrogenase gene (11) The recombinant yeast described.

(17) The recombinant yeast according to (15) or (16), wherein the acetoacetyl CoA transferase gene is a ctfA gene and a ctfB gene derived from Clostridiumacetobutylicum.

(18) The recombinant yeast according to (15) or (16), wherein the acetoacetic acid decarboxylase gene is an adc gene derived from Clostridiumacetobutylicum.

(19) The recombinant yeast according to (15) or (16), wherein the isopropanol dehydrogenase gene is a pdh gene derived from Clostridium beijerinckii.

According to the present invention, a recombinant yeast having an excellent ability to produce isopropanol can be produced by introducing an acetoacetyl-CoA synthase gene and an isopropanol biosynthesis related gene group. In this invention, the manufacturing method of isopropanol excellent in productivity can be provided by utilizing the recombinant yeast which has isopropanol production ability. That is, according to the method for producing isopropanol according to the present invention, productivity in producing isopropanol used as a fuel or resin raw material can be improved, and the production cost of isopropanol can be reduced.

It is a characteristic figure which shows the result of having measured isopropanol production over time about # 15-10 stock, ERG10 / # 15-10 stock, and ORFn / # 15-10 stock.

Hereinafter, the present invention will be described in detail.

The method for producing isopropanol according to the present invention comprises culturing a recombinant yeast into which an acetoacetyl-CoA synthase gene and an isopropanol biosynthesis-related gene group related to a metabolic pathway for synthesizing isopropanol from acetoacetyl-CoA are introduced. To obtain isopropanol.

Acetoacetyl-CoA synthetase gene Acetoacetyl-CoA synthetase gene encodes an enzyme that has the activity of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA, or the activity of synthesizing acetoacetyl-CoA from bimolecular acetyl-CoA It is a gene. An enzyme having an activity of synthesizing acetoacetyl CoA from two molecules of acetyl CoA may be referred to as thiolase.

Particularly in the present invention, it is preferable to use an acetoacetyl-CoA synthase gene encoding an enzyme having an activity of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA. When an acetoacetyl-CoA synthase gene encoding an enzyme that synthesizes acetoacetyl-CoA from malonyl-CoA and acetyl-CoA is used, an enzyme that synthesizes acetoacetyl-CoA from two molecules of acetyl-CoA Compared to the case where the encoded acetoacetyl-CoA synthase gene is used, a recombinant yeast having an excellent ability to produce isopropanol can be produced.

A gene encoding an acetoacetyl-CoA synthase of the type having an activity of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA has been found in, for example, Streptomyces genus actinomycetes (Japanese Patent Laid-Open No. 2008-61506) For example, genes derived from Streptomyces actinomycetes can be used.

Examples of the acetoacetyl CoA synthase gene include a gene encoding a protein having the amino acid sequence of SEQ ID NO: 1. The protein having the amino acid sequence of SEQ ID NO: 1 has an activity of synthesizing acetoacetyl CoA from malonyl CoA and acetyl CoA found in Streptomyces sp. CL190 strain, and acetoacetyl CoA is synthesized from two molecules of acetyl CoA. It is an acetoacetyl-CoA synthase that has no activity to synthesize (Japanese Patent Laid-Open No. 2008-61506).

The gene coding for the protein having the amino acid sequence of SEQ ID NO: 1 uses a pair of primers designed with reference to Japanese Patent Application Laid-Open No. 2008-61506, and a genomic DNA obtained from Streptomyces sp. It can be obtained by a nucleic acid amplification method (for example, PCR).

On the other hand, a gene encoding an acetoacetyl-CoA synthase (thiolase) of a type having an activity of synthesizing acetoacetyl-CoA from bimolecular acetyl-CoA is a conventionally known gene, that is, this type of acetoacetate identified in various organisms. An acetyl-CoA synthase gene can be used. The acetoacetyl CoA synthase gene is a gene included in the mevalonate pathway that exists in many biological species.

An example is a thiolase gene derived from Clostridiumacetobutylicum (deposited as ATCC824). The thiolase gene derived from Clostridium acetobutylicum is expressed as thlA gene and encodes a protein having the amino acid sequence of SEQ ID NO: 2. Examples of thiolase genes that can be used include Schizosaccharomycesypombe, Saccharomyces cerevisiae, Escherichia coli, Macaca mulatta, Bos taurus, Drosophila melanogaster, Oryza sativa, Aspergillus oryzae, Bacillus amyloliquefaciens and Clostridium.

By the way, in the present invention, the acetoacetyl CoA synthase gene is not limited to a gene encoding a protein having the amino acid sequence of SEQ ID NO: 1 derived from Streptomyces sp. And a gene encoding a protein having an amino acid sequence having high similarity and having a function of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA. In the present invention, the acetoacetyl CoA synthase gene is not limited to a thiolase gene encoding a protein having the amino acid sequence of SEQ ID NO: 2 derived from Clostridium acetobutylicum, and has high similarity to the amino acid sequence of SEQ ID NO: 2. And a gene encoding a protein having a function of synthesizing acetoacetyl-CoA from two molecules of acetyl-CoA. Here, high similarity means, for example, a degree of coincidence of 80% or more, preferably a degree of coincidence of 90% or more, more preferably a degree of coincidence of 95% or more, and most preferably a degree of coincidence of 97% or more. To do. The degree of coincidence is calculated when the amino acid sequence of SEQ ID NO: 1 or 2 is aligned with another amino acid sequence using a program for searching for sequence similarity (sometimes referred to as a homology search program). Further, in the other amino acid sequences, the value is calculated as a ratio of amino acid residues that coincide with the amino acid sequence of SEQ ID NO: 1 or 2.

In the present invention, the acetoacetyl CoA synthase gene is a protein having an amino acid sequence in which one or more amino acids in the amino acid sequence of SEQ ID NO: 1 are substituted, deleted, added or inserted, and malonyl CoA And a gene encoding a protein having a function of synthesizing acetoacetyl-CoA from acetyl-CoA. In the present invention, the acetoacetyl CoA synthase gene is a protein having an amino acid sequence in which one or more amino acids in the amino acid sequence of SEQ ID NO: 2 are substituted, deleted, added or inserted, It may be a gene encoding a protein having a function of synthesizing acetoacetyl-CoA from acetyl-CoA. Here, the plurality of amino acids means, for example, 2 to 30 amino acids, preferably 2 to 20, more preferably 2 to 10, and most preferably 2 to 5 amino acids.

Furthermore, in the present invention, the acetoacetyl CoA synthetase gene is a stringent condition for part or all of a polynucleotide comprising a base sequence complementary to the base sequence encoding the amino acid sequence of SEQ ID NO: 1. It may be a polynucleotide that hybridizes below, and that encodes a protein having a function of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA. In the present invention, the acetoacetyl-CoA synthetase gene is a stringent condition for part or all of a polynucleotide comprising a base sequence complementary to the base sequence encoding the amino acid sequence of SEQ ID NO: 2. It may be a polynucleotide that hybridizes underneath and that encodes a protein having a function of synthesizing acetoacetyl-CoA from two molecules of acetyl-CoA. Here, hybridizing under stringent conditions means maintaining binding at 60 ° C. under 2 × SSC washing conditions. Hybridization can be performed by a conventionally known method such as the method described in J. Sambrook et al. Molecular lonCloning, A Laboratory Manual, 2nd Ed., Cold Spring Harbor Laboratory (1989).

A gene encoding an acetoacetyl-CoA synthetase having an amino acid sequence different from the amino acid sequence of SEQ ID NO: 1 as described above can be isolated from actinomycetes other than Streptomyces sp. A gene encoding an acetoacetyl-CoA synthase having an amino acid sequence different from the amino acid sequence of SEQ ID NO: 2 can be isolated from Clostridium bacteria other than Clostridium acetobutylicum (ATCC824), for example. Alternatively, the polynucleotide encoding the amino acid sequence of SEQ ID NO: 1 or 2 can be modified by a technique known in the art. Mutation can be introduced into a nucleotide sequence by a known method such as Kunkel method or Gapped duplex method or a method according thereto, for example, a mutation introduction kit using site-directed mutagenesis (for example, Mutant- Mutations are introduced using K, Mutant-G (both trade names, manufactured by TAKARA) or the like, or using LA PCR in vitro Mutagenesis series kits (trade name, manufactured by TAKARA).

The activity of an acetoacetyl CoA synthase having an amino acid sequence different from the amino acid sequence of SEQ ID NO: 1 can be evaluated as follows. That is, first, a gene encoding a protein to be evaluated is introduced into a host cell so that it can be expressed, and the protein is purified by a technique such as chromatography. Malonyl CoA and acetyl CoA are added as substrates in the obtained buffer containing the protein to be evaluated. Thereafter, for example, incubation is performed at a desired temperature (for example, 10 to 60 ° C.). Then, after the reaction is completed, the function of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA for the protein to be evaluated by measuring the amount of substrate decrease and / or the amount of product (acetoacetyl-CoA) produced Existence and degree can be evaluated. At this time, by adding only acetyl-CoA as a substrate to the obtained buffer containing the protein to be evaluated, and similarly measuring the amount of decrease in the substrate and / or the amount of product produced, bimolecular acetyl The presence or absence of activity of synthesizing acetoacetyl-CoA from CoA can be examined.

The activity of an acetoacetyl CoA synthase having an amino acid sequence different from the amino acid sequence of SEQ ID NO: 2 can be evaluated as follows. That is, first, a gene encoding a protein to be evaluated is introduced into a host cell so that it can be expressed, and the protein is purified by a technique such as chromatography. Acetyl CoA is added as a substrate to the obtained buffer containing the protein to be evaluated. Thereafter, for example, incubation is performed at a desired temperature (for example, 10 to 60 ° C.). After the reaction is completed, the presence or absence of the function of synthesizing acetoacetyl-CoA from bimolecular acetyl-CoA for the protein to be evaluated by measuring the amount of substrate decrease and / or the amount of product (acetoacetyl-CoA) produced And its degree can be evaluated.

Isopropanol biosynthesis related gene group The isopropanol biosynthesis related gene group means a group consisting of a plurality of genes encoding enzymes involved in a metabolic pathway for biosynthesis of isopropanol as a final product using acetoacetyl CoA as a starting compound. . Enzymes involved in the isopropanol biosynthetic metabolic pathway include acetoacetyl-CoA transferase that synthesizes acetylacetate using acetoacetyl-CoA as a substrate, acetoacetate decarboxylase that synthesizes acetone using acetylacetate as a substrate, and isopropanol using acetone as a substrate. An isopropanol dehydrogenase that synthesizes can be mentioned.

Each gene encoding these enzymes can be isolated from a microorganism having the ability to biosynthesize isopropanol. Although it does not specifically limit as microorganisms which have an isopropanol biosynthesis ability, Bacteria can be mentioned. Microorganisms having the ability to biosynthesize isopropanol include microorganisms belonging to the genus Clostridium, including, but not limited to, Clostridium acetobutylicum, Clostridium beijerinckii, Clostridium saccharoperbutylacetonicum, Clostridium saccharoacetobutylicum, Clostridium aurantilos it can. Among them, it is preferable to use an isopropanol biosynthesis-related gene group derived from Clostridium acetobutylicum and Clostridiumijbeijerinckii whose whole genome sequence has been analyzed.

In particular, as the acetoacetyl CoA transferase gene, the ctfA gene and the ctfB gene derived from Clostridiumacetobutylicum can be used. The amino acid sequence of the protein encoded by the ctfA gene is shown in SEQ ID NO: 3, and the amino acid sequence of the protein encoded by the ctfB gene is shown in SEQ ID NO: 4. As the acetoacetate decarboxylase gene, an adc gene derived from Clostridium acetobutylicum can be used. The amino acid sequence of the protein encoded by the adc gene is shown in SEQ ID NO: 5. Furthermore, as the isopropanol dehydrogenase gene, a pdh gene derived from Clostridium 使用 beijerinckii can be used. The amino acid sequence of the protein encoded by the pdh gene is shown in SEQ ID NO: 6.

In addition to the ctfA gene described above, acetoacetyl-CoA transferase (α subunit) genes include, for example, Escherichia coli, Shigella sonnei, Pectobacterium carotovorum, Photorhabdus asymbiotica, Bacillus cereus, Citrobacter koseri, Streptococcus pyogenic, Clostridiumc The gene can be used. In addition to the above-mentioned ctfB gene, genes derived from Escherichia βcoli, Citrobacter koseri, Haemophilus influenzae, Nitrobacter hamburgensis, Streptococcus pyogenes, Clostridium difficile, and Bacillus weihenstephanensis are also used as acetoacetyl CoA transferase (β subunit) genes other than the ctfB gene described above. Can do. In addition to the adc gene, acetoacetate decarboxylase genes include Saccharopolyspora erythraea, Streptomyces avermitilis, Bradyrhizobium sp., Rhizobium leguminosarum, Burkholderia mallei, Ralstonia solanacearum, Francisella tularinii Can do. Furthermore, a gene derived from Rhodococcus rubber can be used as an isopropanol dehydrogenase gene other than the pdh gene.

Further, the isopropanol biosynthesis related gene group is not limited to the above-mentioned genes, and may be homologous genes to the ctfA gene derived from Clostridiumacetobutylicum, the ctfB gene and the adc gene, and the pdh gene derived from Clostridiumbeijerinckii. A homologous gene can be identified by homology search using a known algorithm such as Blast or Fasta against a database storing the base sequence of the gene or the amino acid sequence of the protein. The homologous gene identified using the database can be isolated from a microorganism and used by a known technique. That is, a nucleic acid fragment containing a homologous gene can be obtained by a nucleic acid amplification method using a genomic DNA extracted from a microorganism as a template and a primer designed based on the base sequence of the identified homologous gene.

In addition, a cDNA library is prepared by a known method for the microorganism belonging to the genus Clostridium having the isopropanol biosynthesis ability as described above, and the nucleotide sequence of the ctfA gene derived from Clostridium acetobutylicum, ctfB gene and adc gene, and the pdh gene derived from Clostridium beijerinckii By identifying a cDNA that specifically hybridizes with a probe designed based on the above, a homologous gene derived from a microorganism belonging to the genus Clostridium having the ability to biosynthesize isopropanol as described above can also be obtained.

The method for obtaining homologous genes for the ctfA gene, ctfB gene and adc gene derived from Clostridiumacetobutylicum, and the pdh gene derived from Clostridium beijerinckii is not limited to the method described above, and any method may be applied.

Transformation into host yeast The above-mentioned “acetoacetyl-CoA synthase gene” and “isopropanol biosynthesis related gene group” are incorporated into an appropriate expression vector and introduced into the host yeast. Here, the host yeast is not particularly limited as long as it can express the gene of the present invention. Examples thereof include yeasts such as Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Pichia pastoris.

In addition, when using an acetoacetyl-CoA synthetase gene having an activity of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA, it is preferable to use a yeast having a high oil-fat producing ability. Since malonyl-CoA is part of the substrate in the lipid metabolic pathway, yeast with high oil-fat production capacity has a high synthesis rate and / or amount of malonyl-CoA. Therefore, when using an acetoacetyl-CoA synthase gene that has the activity of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA, an improvement in isopropanol productivity is expected by using yeast with high oil-fat production capacity . Examples of yeasts with high oil and fat production ability include Rhodotorula glutinis, Rhodotorula gracilis, Mortierella alpina, Lipomyces starkeyi, Trichosporon sp.

When yeast is used as a host, the expression vector is preferably capable of autonomous replication in the host yeast, and at the same time comprises a promoter, a ribosome binding sequence, the above-described gene, and a transcription termination sequence. The expression vector may contain a gene that controls promoter activity.

In addition, the above-mentioned “acetoacetyl CoA synthase gene” and “isopropanol biosynthesis related gene group” are preferably introduced into the chromosome of the host yeast. In a recombinant yeast in which these genes are introduced onto the chromosome, these genes can be stably and highly expressed, and an excellent isopropanol producing ability can be achieved. In addition, in order to introduce | transduce these genes on a chromosome, it does not specifically limit, A conventionally well-known method can be used suitably. As an example, a method utilizing homologous recombination with a host yeast chromosome can be used.

In addition, it is preferable that the above-mentioned “acetoacetyl CoA synthase gene” and “isopropanol biosynthesis related gene group” are introduced in multiple copies on the chromosome of the host yeast. In a recombinant yeast in which these genes are introduced in multiple copies on a chromosome, these genes are highly expressed, and an excellent isopropanol production ability can be achieved. In addition, in order to introduce | transduce these genes by multiple copies on a chromosome, it does not specifically limit, A conventionally well-known method can be used suitably. As an example, a method using a multi-copy introduction type vector can be mentioned.

When yeast is used as a host, for example, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Pichia pastoris and the like are used. In this case, the promoter is not particularly limited as long as it can induce expression in yeast. For example, gal1 promoter, gal10 promoter, heat shock protein promoter, MFα1 promoter, PHO5 promoter, PGK promoter, GAP promoter, ADH promoter, AOX1 promoter Etc.

The method for introducing the recombinant vector into yeast is not particularly limited as long as it is a method for introducing DNA into yeast. For example, the electroporation method [Becker, DM, et.al .: Methods. Enzymol., 194: 182- 187 (1990)], spheroplast method [Hinnen, A. et al.:Proc. Natl. Acad. Sci., USA, 75: 1929-1933 (1978)], lithium acetate method [Itoh, H .: J .Bacteriol., 153: 163-168 (1983)].

Further, the host yeast may have at least one endogenous gene among the above-mentioned “isopropanol biosynthesis-related genes”. In this case, it is only necessary to introduce genes other than the endogenous gene among the above-mentioned “isopropanol biosynthesis-related genes”.

Production of isopropanol By culturing the recombinant yeast introduced with the above-mentioned “acetoacetyl-CoA synthase gene” and “isopropanol biosynthesis related gene group” in a medium containing a carbon source such as glucose, the biosynthesis of isopropanol is achieved. proceed. In general, there are many cases where the intended purpose cannot be achieved even if a predetermined gene is introduced into yeast for the purpose of imparting or enhancing the ability to produce the target substance. The reason is that it is difficult to stably express a gene derived from a foreign species in a sufficient amount. In addition, there may be a possibility that a sufficient amount of acetoacetyl-CoA is not present in the cell to biosynthesize isopropanol. For example, when two molecules of acetyl CoA are combined by thiolase to synthesize acetoacetyl CoA, the equilibrium of this reaction is directed to the direction in which acetyl CoA is synthesized from acetoacetyl CoA. Therefore, it is considered difficult to proceed in the direction of acetoacetyl-CoA synthesis unless there is a strong reaction for converting the synthesized acetoacetyl-CoA to the next substance.

The culture conditions for culturing yeast introduced with the above-mentioned “acetoacetyl-CoA synthase gene” and “isopropanol biosynthesis related gene group” are not particularly limited, and auxotrophy and drug resistance of the host yeast are not limited. The culture medium may be used under normal conditions.

Since the synthesized isopropanol is present in the medium, isopropanol can be obtained from the supernatant fraction after separating the cells from the medium by means such as centrifugation. In order to isolate isopropanol from the supernatant fraction, for example, an organic solvent such as ethyl acetate and methanol is added to the supernatant fraction and sufficiently stirred. It can isolate | separate into an aqueous layer and a solvent layer, and isopropanol can be extracted from a solvent layer.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the technical scope of the present invention is not limited to the following examples.

[Example 1]
In this Example, Streptomyces sp. CL190 strain ORFn gene or Saccharomyces cerevisiae ERG10 gene as acetoacetyl CoA synthase gene, Clostridium acetobutylicum ctfA gene and ctfB gene as acetoacetyl CoA transferase gene, acetoacetate A recombinant yeast was prepared by introducing an adc gene derived from Clostridium acetobutylicum as a decarboxylase and a pdh gene derived from Clostridium beijerinckii as an isopropanol dehydrogenase gene, and the isopropanol production ability was examined.

The ORFn gene encodes an acetoacetyl-CoA synthase having an activity of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA. The ERG10 gene encodes an acetoacetyl-CoA synthase having an activity of synthesizing acetoacetyl-CoA from two molecules of acetyl-CoA.

In this example, first, an expression vector (pEXP (Ura) -ADC-CTFA-CTFB) having a ctfA gene, a ctfB gene and an adc gene is used to introduce these genes into a chromosome, and recombination is excellent in acetone production ability. Yeast was selected. Thereafter, the selected recombinant yeast was further introduced into a chromosome using an expression vector (pDI626PGK-T-iPDH) having the pdh gene, and a recombinant yeast excellent in isopropanol production ability was selected. Next, one of the genes is further introduced into the chromosome using the expression vector having the ORFn gene (pESCpgkgap-HIS-ORFn) or the expression vector having the ERG10 gene (pESCpgkgap-HIS-ERG10) to the selected recombinant yeast. Then, isopropanol production ability was evaluated.

In this example, Saccharomyces cerevisiae YPH499 (Stratagene) was used as the yeast. The following medium was used for the culture of YPH499.

YPD medium
2% Bacto Peptone (manufactured by DIFCO)
1% Bacto Yeast extract (manufactured by DIFCO)
2% D-Glucose (Wako Pure Chemical Industries)
SD (-URA-TRP-HIS)
SD medium was manufactured by BIO101. As the SD (-URA-TRP-HIS) medium, SD medium excluding uracil, tryptophan and histidine was used.

The genomic DNA of yeast YPH499 was prepared according to the following method. First, Saccharomyces cerevisiae YPH499 (Stratagene) was cultured in 3 ml of YPD medium at 30 ° C for 1 day. 1.5 ml of the culture solution was subjected to a genomic DNA preparation kit (Gentra Puregene Yeast / Bact.kit) manufactured by QIAGEN to prepare genomic DNA.

<Preparation of pESCpgkgap-HIS-ORFn>
Preparation of pDI626PGKpro PCR was performed under the following conditions.

Primer (50 pmol):
SacI-Ppgk1 FW; 5'TAG GGA GCT CCA AGA ATT ACT CGT GAG TAA GG 3 '(SEQ ID NO: 7)
SacII-Ppgk1 RV; 5'ATA ACC GCG GTG TTT TAT ATT TGT TGT AAA AAG TAG 3 '(SEQ ID NO: 8)
Template: Yeast YPH499 genomic DNA (0.4μg)
Reaction solution: 1x Pfu Ultra II reaction buffer (Stratagene); 10 nmol dNTP; 1 μl Pfu Ultra II fusion HS DNA polymerase (Stratagene); 50 μl solution reaction: 95 ° C 5 min- (95 ° C 30 sec, 55 ° C 30 sec 72 ° C., 2 minutes) × 25 cycles—72 ° C., 3 minutes—4 ° C. After the completion of the PCR reaction, the reaction solution was purified using a MinElute PCR purification kit manufactured by QIAGEN. The obtained amplified fragment was digested with restriction enzymes SacI and SacII. Agarose gel electrophoresis was performed, and a 712 bp fragment was excised and purified using a MinElute Gel extraction kit manufactured by QIAGEN. Similarly, it was ligated to a pDI626GAP ((APP. Env. Micro., 2009, 5536-5543)) vector digested with restriction enzymes SacI and SacII. The obtained sequence was sequenced to confirm that the target plasmid was prepared. The plasmid thus obtained was named pDI626PGKpro.

Preparation of pDI626PGK PCR was performed under the following conditions.

Primer (50 pmol):
SalI-Tpgk1 FW; 5'TTA AGT CGA CAT TGA ATT GAA TTG AAA TCG ATA GAT C 3 '(SEQ ID NO: 9)
KpnI-Tpgk1 RV2; 5'TTA AGG TAC CGC TTC AAG CTT ACA CAA CAC 3 '(SEQ ID NO: 10)
Template: Yeast YPH499 genomic DNA (0.4μg)
Reaction solution: 1x Pfu Ultra II reaction buffer (Stratagene); 10 nmol dNTP; 1 μl Pfu Ultra II fusion HS DNA polymerase (Stratagene); 50 μl solution reaction: 95 ° C 5 min- (95 ° C 30 sec, 55 ° C 30 sec 72 ° C., 2 minutes) × 25 cycles—72 ° C., 3 minutes—4 ° C. After completion of the stock PCR reaction, the reaction solution was purified using MinElute PCR purification kit manufactured by QIAGEN, and then digested with restriction enzymes SalI and KpnI. Agarose gel electrophoresis was performed, and a 330 bp fragment was excised and purified using MinElute Gel extraction kit manufactured by QIAGEN. The pDI626PGKpro vector was digested with the restriction enzymes SalI and KpnI. The obtained sequence was sequenced to confirm that the target plasmid was prepared. The plasmid thus obtained was named pDI626PGK.

Preparation of pDI626PGK-T The above pDI626PGK was digested with the restriction enzyme SbfI, and the reaction solution was purified using MinElute PCR purification kit manufactured by QIAGEN. Thereafter, the ends were blunted using a TaKaRaBIO Blunting kit and further digested with the restriction enzyme KpnI. Agarose gel electrophoresis was performed, and a 3650 bp fragment was excised and purified using MinElute Gel extraction kit manufactured by QIAGEN. This was used as a vector for ligation. Next, pRS524GAP (APP. Env. Micro., 2009, 5536-5543) was digested with restriction enzymes PmaCI and KpnI. Agarose gel electrophoresis was performed, and a 765 bp fragment was excised and purified using a MinElute Gel extraction kit manufactured by QIAGEN to obtain an insert. These ligations were performed, and the obtained sequence was sequenced to confirm that the target plasmid was prepared. The plasmid thus obtained was designated as pDI626PGK-T.

Preparation of pESCgap-HIS PCR was performed under the following conditions.

Primer (50 pmol):
EcoRI-Pgap-F; 5'CAC GGA ATT CCA GTT CGA GTT TAT CAT TAT CAA 3 '(SEQ ID NO: 11)
BamHI-Pgap-R; 5 'CTC TGG ATC CTT TGT TTG TTT ATG TGT GTT TAT TC 3' (SEQ ID NO: 12)
Template: pDI626GAP plasmid (1ng)
Reaction solution: 1x Pfu Ultra II reaction buffer (Stratagene); 10 nmol dNTP; 1 μl Pfu Ultra II fusion HS DNA polymerase (Stratagene); 50 μl solution reaction: 95 ° C. 2 minutes- (95 ° C. 30 seconds, 55 ° C. 30 seconds 72 ° C., 2 minutes) × 25 cycles—72 ° C., 3 minutes—4 ° C. After completion of the PCR reaction, the reaction solution was purified using the MinElute PCR purification kit manufactured by QIAGEN, and then digested with restriction enzymes BamHI and EcoRI. Agarose gel electrophoresis was performed, and a 686 bp fragment was excised and purified using a MinElute Gel extraction kit manufactured by QIAGEN. It was ligated to a pESC-HIS (purchased from STRATAGENE) vector digested with restriction enzymes BamHI and EcoRI. The obtained sequence was sequenced to confirm that the target plasmid was prepared. The plasmid thus obtained was named pESCgap-HIS.
Preparation of pESCpgkgap-HIS PCR was performed under the following conditions.

Primer (50 pmol):
MunI-Ppgk1-F; 5'TAG GCA ATT GCA AGA ATT ACT CGT GAG TAA GG 3 '(SEQ ID NO: 13)
EcoRI-Ppgk1-R; 5'ATA AGA ATT CTG TTT TAT ATT TGT TGT AAA AAG TAG 3 '(SEQ ID NO: 14)
Template: pDI626PGK plasmid (1ng)
Reaction solution: 1x Pfu Ultra II reaction buffer (Stratagene); 10 nmol dNTP; 1 μl Pfu Ultra II fusion HS DNA polymerase (Stratagene); 50 μl solution reaction: 95 ° C. 2 minutes- (95 ° C. 30 seconds, 55 ° C. 30 seconds 72 ° C., 2 minutes) × 25 cycles—72 ° C., 3 minutes—4 ° C. After completion of the stock PCR reaction, the reaction solution was purified using the MinElute PCR purification kit manufactured by QIAGEN, and then digested with restriction enzymes MunI and EcoRI. Agarose gel electrophoresis was performed, and a 718 bp fragment was excised and purified using a MinElute Gel extraction kit manufactured by QIAGEN. The pESCgap-HIS vector was digested with the restriction enzyme EcoRI and BAP-treated, and then ligated. It was confirmed by colony PCR that the insert was ligated in the correct direction, and a plasmid was prepared. The sequence was sequenced and it was confirmed that the target plasmid was prepared. The plasmid thus obtained was named pESCpgkgap-HIS.

Construction of pCR2.1-ORFn Based on the base sequence of ORFn gene derived from Streptomyces sp. CL190 strain, it was designed so that the rare codon in Saccharomyces cerevisiae contained in this base sequence is a codon with high frequency of appearance. The designed base sequence is shown in SEQ ID NO: 15. In this example, a nucleic acid fragment consisting of the designed base sequence was synthesized. Moreover, the synthetic | combination DNA sequence of ggcccgccacc (sequence number 16) was provided to the upstream untranslated region of the synthetic | combination ORFn gene, and the synthetic | combination DNA sequence of ctcgag was provided to the downstream untranslated region. This synthetic gene was introduced into plasmid pCR2.1 (manufactured by Invitrogen), and the resulting plasmid was named pCR2.1-ORFn.

Preparation of pESCpgkgap-HIS-ORFn After digesting the above pCR2.1-ORFn with restriction enzymes BamHI and XhoI, a 1002 bp fragment was excised and similarly ligated to the above pESCpgkgap-HIS vector digested with restriction enzymes BamHI and XhoI. The obtained sequence was analyzed with a restriction enzyme, and it was confirmed that the target plasmid was prepared. The plasmid thus obtained was named pESCpgkgap-HIS-ORFn. pESCpgkgap-HIS-ORFn is a vector for introducing an ORFn gene derived from Streptomyces sp. strain CL190, which is codon designed to be optimally expressed in Saccharomyces cerevisiae YPH499, onto the chromosome of Saccharomyces cerevisiae YPH499. This ORFn gene is regulated by the PGK promoter and is constitutively expressed.

<Preparation of pESCpgkgap-HIS-ERG10>
PCR was performed under the following conditions.

Primer (50 pmol):
ERG10-F; 5'GGG GGG ATC CGC CAC CAT GTC TCA GAA CGT TTA CAT TGT ATC 3 '(SEQ ID NO: 17)
ERG10-R; 5'GGG GCT CGA GTC ATA TCT TTT CAA TGA CAA TAG AGG 3 '(SEQ ID NO: 18)
Template: YPH499 genomic DNA (0.3μg)
Reaction solution: 1x Pfu Ultra II reaction buffer (Stratagene); 10 nmol dNTP; 1 μl Pfu Ultra II fusion HS DNA polymerase (Stratagene); 50 μl solution reaction: 95 ° C 5 min- (95 ° C 30 sec, 55 ° C 30 sec 72 ° C., 2 minutes) × 30 cycles—72 ° C., 3 minutes—4 ° C. After completion of the PCR reaction, the reaction solution was purified using MinElute PCR purification kit manufactured by QIAGEN, and then digested with restriction enzymes BamHI and XhoI. After agarose gel electrophoresis, a 1209 bp fragment was excised and purified using a MinElute Gel extraction kit manufactured by QIAGEN. The obtained DNA fragment was ligated to the pESCpgkgap-HIS vector digested with restriction enzymes BamHI and XhoI. The sequence was sequenced and it was confirmed that the target plasmid was prepared. The plasmid thus obtained was named pESCpgkgap-HIS-ERG10. pESCpgkgap-HIS-ERG10 is a vector for introducing a thiolase gene derived from Saccharomyces cerevisiae YPH499 onto the chromosome of Saccharomyces cerevisiae YPH499. This ORFn gene is regulated by the PGK promoter and is constitutively expressed.

<Preparation of pEXP (Ura) -ADC-CTFA-CTFB>
The adc gene, ctfA gene and ctfB gene derived from Clostridium acetobutylicum ATCC824 strain were each cloned into pT7Blue vector. After cloning the obtained vector into pDI626, entry clones (pENT-ADC, pENT-CTFA and pENT-CTFB) were prepared using a Gateway donor vector (Invitrogen). Then, pEXP (Ura) -ADC-CTFA-CTFB was produced by incorporating the obtained entry clone into an expression vector (pDEST626 (2008)). Details are as follows.

Preparation of pENT-ADC An entry clone of the adc gene (pENT-ADC) was prepared as follows.

First, PCR was performed under the following conditions.

Primer (50 pmol):
adc-F; 5'ATG TTA AAG GAT GAA GTA ATT AAA CAA ATT AG 3 '(SEQ ID NO: 19)
adc-R; 5'TTA CTT AAG ATA ATC ATA TAT AAC TTC AGC TC 3 '(SEQ ID NO: 20)
Template: Genomic DNA of the above ATCC824 strain (0.4μg)
Reaction solution: 1 × Pfu Ultra II reaction buffer (Stratagene); 10 nmol dNTP; 1 μl Pfu Ultra II fusion HS DNA polymerase (Stratagene); 50 μl solution reaction: 95 ° C. 5 minutes- (95 ° C. 30 seconds, 60 ° C. 30 seconds 72 ° C. 2 minutes) × 30 cycles −72 ° C. 3 minutes −4 ° C. A 735 bp fragment amplified by stock PCR was blunt-end cloned into the pT7Blue vector (Takara Bio) using the Perfectly Blunt Cloning Kit manufactured by Novagen. The cloned sequence was sequenced and confirmed to be the base sequence (CA-P0165) of the adc gene of Clostridium acetobutylicum ATCC824 strain. The plasmid thus obtained was named pT7Blue-ADC.

Next, pT7Blue-ADC was digested with restriction enzymes BamHI and SalI, and a 771 bp fragment was excised and ligated to the pDI626 vector similarly digested with restriction enzymes BamHI and SalI. The obtained sequence was sequenced to confirm that the target plasmid was prepared. The plasmid thus obtained was named pDI626-ADC.

Next, PCR was performed with the following primers using the obtained pDI626-ADC as a template.

Primer:
08-189-adc-attB1-Fw; 5'GGG GAC AAG TTT GTA CAA AAA AGC AGG CTC AGT TCG AGT TTA TCA TTA TC 3 '(SEQ ID NO: 21)
08-189-adc-attB4-Rv; 5'GGG GAC AAC TTT GTA TAG AAA AGT TGG GTG GGC CGC AAA TTA AAG CCT TC 3 '(SEQ ID NO: 22)
The obtained 1809 bp PCR product was introduced into the donor vector pDONR221 P1-P4 by gateway BP reaction. The obtained clone was sequenced, and it was confirmed that there was no mutation in the entire base sequence of the insert. The plasmid thus obtained was named pENT-ADC.

Preparation of pENT-CTFA An entry clone (pENT-CTFA) of ctfA gene was prepared as follows.

First, PCR was performed under the following conditions.

Primer (50 pmol):
ctfA-F; 5'ATG AAC TCT AAA ATA ATT AGA TTT GAA AAT TTA AGG 3 '(SEQ ID NO: 23)
ctfA-R; 5'TTA TGC AGG CTC CTT TAC TAT ATA ATT TA 3 '(SEQ ID NO: 24)
Template: Genomic DNA of the above ATCC824 strain (0.4μg)
Reaction solution: 1 × Pfu Ultra II reaction buffer (Stratagene); 10 nmol dNTP; 1 μl Pfu Ultra II fusion HS DNA polymerase (Stratagene); 50 μl solution reaction: 95 ° C. 5 minutes- (95 ° C. 30 seconds, 60 ° C. 30 seconds , 72 ° C., 2 minutes) × 30 cycles—72 ° C., 3 minutes—4 ° C. A 657 bp fragment amplified by stock PCR was similarly cloned using a Perfectly Blunt Cloning Kit manufactured by Novagen. The cloned sequence was sequenced and confirmed to be the base sequence (CA-P0163) of the ctfA gene of Clostridium acetobutylicum ATCC824 strain. The plasmid thus obtained was named pT7Blue-CTFA.

Next, pT7Blue-CTFA was digested with restriction enzymes BamHI and SalI, a 693 bp fragment was excised, and ligated to the pDI626PGK vector similarly digested with restriction enzymes BamHI and SalI. The obtained sequence was sequenced to confirm that the target plasmid was prepared. The plasmid thus obtained was named pDI626PGK-CTFA.

Next, PCR was performed using the obtained pDI626PGK-CTFA as a template and the following primers.

Primer:
08-189-ctfA-attB4r-Fw; 5'GGG GAC AAC TTT TCT ATA CAA AGT TGG CTT CAA GCT TAC ACA ACA CGG 3 '(SEQ ID NO: 25)
08-189-ctfA-attB3r-Rv; 5'GGG GAC AAC TTT ATT ATA CAA AGT TGT CAA GAA TTA CTC GTG AGT AAG G 3 '(SEQ ID NO: 26)
The obtained 1823 bp PCR product was introduced into the donor vector pDONR221 P4r-P3r by gateway BP reaction. The obtained clone was sequenced, and it was confirmed that there was no mutation in the entire base sequence of the insert. The plasmid thus obtained was named pENT-CTFA.

Preparation of pENT-CTFB An entry clone (pENT-CTFB) of ctfB gene was prepared as follows.

First, PCR was performed under the following conditions.

Primer (50 pmol):
ctfB-F; 5'ATG ATT AAT GAT AAA AAC CTA GCG AAA G 3 '(SEQ ID NO: 27)
ctfB-R; 5 'CTA AAC AGC CAT GGG TCT AAG TTC 3' (SEQ ID NO: 28)
Template: Genomic DNA of the above ATCC824 strain (0.4μg)
Reaction solution: 1 × Pfu Ultra II reaction buffer (Stratagene); 10 nmol dNTP; 1 μl Pfu Ultra II fusion HS DNA polymerase (Stratagene); 50 μl solution reaction: 95 ° C. 5 minutes- (95 ° C. 30 seconds, 60 ° C. 30 seconds , 72 ° C., 2 minutes) × 30 cycles—72 ° C., 3 minutes—4 ° C. A 666 bp fragment amplified by stock PCR was cloned using a Perfectly Blunt Cloning Kit manufactured by Novagen. The cloned sequence was sequenced and confirmed to be the base sequence (CA-P0164) of the ctfB gene of Clostridium acetobutylicum ATCC824 strain. The plasmid thus obtained was named pT7Blue-CTFB.

Next, pT7Blue-CTFB was digested with restriction enzymes BamHI and SalI, and a 771 bp fragment was excised and ligated to the pDI626 vector similarly digested with restriction enzymes BamHI and SalI. The obtained sequence was sequenced to confirm that the target plasmid was prepared. The plasmid thus obtained was named pDI626-CTFB (+ A).

Next, PCR was performed under the following conditions using the following primers in order to correct the mutation sites in the primers.

Primer (50 pmol):
BamHI-ctfB-F; 5'TAG TGG ATC CGA TGA TTA ATG ATA AAA ACC 3 '(SEQ ID NO: 29)
pDI626MCS-seqF; 5'CCT AGA CTT CAG GTT GTC TAA C 3 '(SEQ ID NO: 30)
Mold: pDI626-CTFB (+ A) (1 ng)
Reaction solution: 1x Pfu Ultra II reaction buffer (Stratagene); 10 nmol dNTP; 1 μl Pfu Ultra II fusion HS DNA polymerase (Stratagene); 50 μl solution reaction: 95 ° C. 2 minutes- (95 ° C. 30 seconds, 55 ° C. 30 seconds , 72 ° C. for 1 minute) × 20 cycles −72 ° C. for 3 minutes to 4 ° C. After completion of the PCR reaction, the reaction solution was purified using the MinElute PCR purification kit manufactured by QIAGEN, and then digested with restriction enzymes BamHI and SalI. Agarose gel electrophoresis was performed, and a 702 bp fragment was excised and purified using a MinElute Gel extraction kit manufactured by QIAGEN. The pDI626 vector digested with restriction enzymes BamHI and SalI was ligated. The obtained sequence was sequenced to confirm that the mutation site was corrected. The plasmid thus obtained was named pDI626-CTFB.

Next, PCR was performed using pDI626-CTFB as a template and the following primers.

Primer:
08-189-ctfB-attB3-Fw; 5'GGG GAC AAC TTT GTA TAA TAA AGT TGG GCC GCA AAT TAA AGC CTT C 3 '(SEQ ID NO: 31)
08-189-ctfB-attB2-Rv; 5'GGG GAC CAC TTT GTA CAA GAA AGC TGG GTA CAG TTC GAG TTT ATC ATT ATC 3 '(SEQ ID NO: 32)
The obtained 1737 bp PCR product was introduced into the donor vector pDONR221 P3-P2 by gateway BP reaction. The obtained clone was sequenced, and it was confirmed that there was no mutation in the entire base sequence of the insert. The plasmid thus obtained was named pENT-CTFB.

Preparation of pDEST626 (2008) PCR was performed under the following conditions.

Primer:
SacI-convA-F; 5'TAG GGA GCT CAT CAC AAG TTT GTA CAA AAA AGC TG 3 '(SEQ ID NO: 33)
KpnI-convA-R; 5'TTA AGG TAC CAT CAC CAC TTT GTA CAA GAA AGC 3 '(SEQ ID NO: 34)
Mold: RfA (Invitrogen Gateway Vector Conversion System) (0.5 ng)
Primer (50 pmol):
Reaction solution: 1x Pfu Ultra II reaction buffer (Stratagene); 10 nmol dNTP; 1 μl Pfu Ultra II fusion HS DNA polymerase (Stratagene); 50 μl solution reaction: 95 ° C. 2 minutes- (95 ° C. 30 seconds, 55 ° C. 30 seconds 72 ° C 1 minute 30 seconds) x 20 cycles-72 ° C 3 minutes -4 ° C stock The RfA used as a template is Reading Frame Cassette A of Gateway Vector Conversion System. After completion of the PCR reaction, the reaction solution was purified using a MinElute PCR purification kit manufactured by QIAGEN and then digested with restriction enzymes SacI and KpnI. Perform agarose gel electrophoresis, excise the 1717 bp fragment, purify it using the QIAGEN MinElute Gel extraction kit, and then ligate it to the pDI626GAP vector (APP. Env. Micro., 2009, 5536) digested with the restriction enzymes SacI and KpnI. did. The obtained sequence was sequenced to confirm that the target plasmid was prepared. The plasmid thus obtained was named pDEST626 (2008).

Preparation of pEXP (Ura) -ADC-CTFA-CTFB
Three entry clones (pENT-ADC, pENT-CTFA and pENT-CTFB) obtained as described above were incorporated into the expression vector pDEST626 (2008) by Gateway LR reaction. About the obtained clone, insert size was confirmed by PCR and it confirmed that recombination was correctly performed. A sequence was performed and it was confirmed that there was no error in the array. The thus obtained plasmid was designated as pEXP (Ura) -ADC-CTFA-CTFB.

<Production of pDI626PGK-T-iPDH>
Preparation of pCR2.1-iPDH First, based on the base sequence of pdh gene derived from Clostridium beijerinckii NRRL B593 registered in GenBank, the rare codon in Saccharomyces cerevisiae contained in this base sequence is used as a codon with high frequency of appearance. Designed as follows. In this example, a nucleic acid fragment consisting of the designed base sequence was synthesized (SEQ ID NO: 35). Further, a synthetic DNA sequence of GGGGTTTCCGCGGTCTAGAGCCACC (SEQ ID NO: 36) was assigned to the upstream untranslated region of the synthesized pdh gene, and GGATCCGTCGACGGGG (SEQ ID NO: 37) was assigned to the downstream untranslated region. This plasmid was named pCR2.1-iPDH.

Preparation of pDI626PGK-T-iPDH Next, pCR2.1-iPDH was digested with restriction enzymes SacII and SalI, a 1080 bp fragment was excised and similarly ligated to the above pDI626PGK-T vector digested with restriction enzymes SacII and SalI. . The obtained sequence was sequenced to confirm that the target plasmid was prepared. The plasmid thus obtained was designated as pDI626PGK-T-iPDH. pDI626PGK-T-iPDH is a vector for introducing the pdh gene derived from Clostridium beijerinckii NRRL B593 strain, which is codon designed to be optimally expressed in Saccharomyces cerevisiae YPH499, onto the chromosome of Saccharomyces cerevisiae YPH499. This pdh gene is regulated by the PGK promoter and is constitutively expressed.

<Transformation 1>
In this example, first, pEXP (Ura) -ADC-CTFA-CTFB constructed as described above was linearized by cutting with restriction enzymes AatII and BssHII, and after ethanol precipitation, dissolved in 0.1 × TE Buffer, Saccharomyces cerevisiae YPH499 (Stratagene) was transformed using Frozen EZ yeast transformation kit (Zymoresearch). The obtained clones were subjected to colony PCR, and it was confirmed that adc gene, ctfA gene and ctfB gene were introduced in 25 clones. Moreover, the acetone production amount in the obtained clone was measured, and the strain with the highest acetone production amount was named # 3-17.

<Transformation 2>
In this example, next, pDI626PGK-T-iPDH constructed as described above was linearized by cutting with restriction enzymes AatII and BssHII, and after ethanol precipitation, dissolved in 0.1 × TE Buffer, Frozen EZ yeast transformation kit (Zymoresearch) was used to transform acetone-producing yeast # 3-17. The resulting 14 clones were subjected to colony PCR, and it was confirmed that the pdh gene was introduced in 13 clones. The amount of isopropanol produced in the obtained clones was measured, and the strain with the highest isopropanol production was named # 15-10.

<Transformation 3>
In this example, # 15-10 was then transformed with pESCpgkgap-HIS-ERG10 (0.5 μg) constructed as described above. The transformation method followed the method of Frozen EZ yeast transformation kit (manufactured by Zymoresearch) as described above. After the transformation treatment, it was applied to an SD (-URA-TRP-HIS) medium, cultured for 5 days at 30 ° C., and the colonies that appeared were passaged. After confirming that the ERG10 gene was introduced by PCR, the obtained strain was named ERG10 / # 15-10 strain.
Similarly, # 15-10 was transformed with pESCpgkgap-HIS-ORFn (0.5 μg) constructed as described above. After confirming that the ORFn gene was introduced by PCR, the obtained strain was named ORFn / # 15-10 strain.

<Isopropanol productivity test>
Isopropanol productivity was evaluated for the recombinant yeast (ERG10 / # 15-10 strain and ORFn / # 15-10 strain) prepared in the above-described Transformation 3. Specifically, first, 30 μl of a recombinant yeast solution thawed from a glycerol stock was inoculated into a disposable glass test tube (16 × 100 mm, manufactured by ASAHI TECHNO GLASS) containing 3 ml of a medium. The test tube was shaken for 66 hours at 30 ° C., 130 strokes / min (Takasaki 2-stage shaking incubator TXY-16R-2FL type) to prepare a preculture solution. Next, 1 ml of the preculture was inoculated into a 300 ml Erlenmeyer flask containing 100 ml of the medium, and rotated and cultured at 30 ° C. and 130 rpm for 240 hours in an Oriental Giken two-stage incubator (IFM-I IS type). After starting the main culture, OD600 nm was measured at 24H, 48H, 72H, 96H, 168H, and 240H, and sampling was performed.

3 ml of the culture solution was put into a test tube with a screw cap (TST SCR-16-100; 16 × 100 mm ASAHI TECHNO GLASS) and centrifuged at room temperature for 5 minutes at 1000 g (TOMY LC-230 type). 2 ml of the supernatant was put into a 20 ml HSS vial and fastened, followed by heat treatment at 60 ° C. for 15 minutes. Thereafter, acetone and isopropanol were analyzed by HSS-GC / MS analysis. The concentration of the sample was quantified by preparing a standard solution with a known concentration in advance and drawing a calibration curve. The analysis conditions for HSS-GC / MS are shown below.

Headspace sampler analysis conditions Headspace sampler: HP7694 (Hewlett-Packard)
Zone Temp.
Oven: 60 ℃
Loop ； 150 ℃
TR.LINE; 200 ℃
Event Time:
GC CYCLE TIME; 35 min
Vial EQ TIME; 15min
PRESSURIZ. TIME; 0.50min
Loop Fill TIME; 0.2min
Loop EQ TIME; 0.2min
INJECT TIME; 1.00 min
Vial Prameter
SHAKE ； HIGH
Other vial pressurization; 15psi
Loop size: 3ml
GC-MS analysis conditions GC / MS: HP6890 / 5973 GC / MS system (Hewlett-Packard)
Column used: J & W DB-624 (0.32mm x 60m, film thickness 1.8μm)
Inlet temperature: 260 ℃
Detector temperature: 260 ° C
Injection parameters:
Split ratio; 1/20
Carrier gas: Helium 1.0 ml / min Oven heating conditions: 5 minutes at 40 ° C → Heat to 75 ° C at 5 ° C / minute → Heat to 260 ° C at 100 ° C / minute → 16 minutes at 260 ° C <Measurement results>
For the # 15-10 strain prepared in the above-described transformation 2, the ERG10 / # 15-10 strain and the ORFn / # 15-10 strain prepared in the above-described transformation 3, the measurement results of isopropanol production over time are shown. As shown in FIG. In FIG. 1, the downward triangle indicates the # 15-10 strain, the upward triangle indicates the ERG10 / # 15-10 strain, and the black circle indicates the ORFn / # 15-10 strain. Table 1 shows the result of comparing the amount of isopropanol produced in 96 hours after the start of the main culture.

As can be seen from FIG. 1 and Table 1, an acetoacetyl-CoA synthase gene was further introduced into a recombinant yeast into which isopropanol biosynthesis-related genes related to the metabolic pathway for synthesizing isopropanol from acetoacetyl-CoA were introduced. It was revealed that the recombinant yeast can greatly improve the productivity of isopropanol. In particular, when an acetoacetyl-CoA synthetase gene encoding an enzyme having an activity of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA is introduced, it has an activity of synthesizing acetoacetyl-CoA from two molecules of acetyl-CoA Compared to the case where an acetoacetyl CoA synthase gene (thiolase) encoding an enzyme was introduced, the productivity of isopropanol was dramatically improved. This was thought to be because the yeast used as the host inherently had lipid synthesis ability and inherently sufficient malonyl-CoA used for this lipid synthesis pathway. Therefore, from this result, for yeast having excellent lipid synthesis ability, acetoacetyl-CoA synthase gene encoding an enzyme having an activity of synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA and isopropanol from acetoacetyl-CoA It was found that recombinant yeast having higher isopropanol productivity can be produced by introducing an isopropanol biosynthesis related gene group related to a metabolic pathway for synthesizing.

[Reference Example 1]
In this reference example, Escherichia coli is used as a host, and an recombinant acetoacetyl-CoA synthase gene is introduced into a recombinant Escherichia coli that has been introduced with an isopropanol biosynthesis-related gene group related to the metabolic pathway for synthesizing isopropanol from acetoacetyl-CoA. The introduced recombinant Escherichia coli was prepared, and isopropanol productivity was evaluated.

<Preparation of genomic DNA of Clostridium acetobutylicum>
Clostridium acetobutylicum ATCC (824) strain was anaerobically cultured in 3 ml of Difco clostridium enriched medium according to a conventional method for 2 days. Genomic DNA was prepared from 1.5 ml of the culture solution using a genomic DNA preparation kit (Gentra Puregene Yeast / Bact. Kit) manufactured by QIAGEN.

<Preparation of pT7Blue-CAC2873>
The thiA gene, a thiolase gene derived from Clostridium acetobutylicum, was cloned as follows. First, PCR was performed using the following primers.

CAC2873-F: 5'-ATG AAA GAA GTT GTA ATA GCT AGT GCA G-3 '(SEQ ID NO: 38)
CAC2873-R: 5'-CTA GCA CTT TTC TAG CAA TAT TGC TG-3 '(SEQ ID NO: 39)
As a template in PCR, 0.1 μg of the genomic DNA of Clostridium acetobutylicum ATCC (824) prepared above was used. The pair of primers was 50 pmol. The composition of the reaction solution was a 50 μl solution containing 10 nmol of dNTP and 1 μl of Pfu Ultra II fusion HS DNA polymerase (Stratagene) in 1 × Pfu Ultra II reaction buffer (Stratagene). The PCR thermal cycle was performed at 95 ° C. for 5 minutes, followed by 30 cycles of 95 ° C. for 30 seconds, 60 ° C. for 30 seconds and 72 ° C. for 3 minutes, followed by 72 ° C. for 3 minutes. After the reaction, the stock was stored at 4 ° C.

The approximately 1.2 kb fragment amplified by PCR was blunt-end cloned into the pT7-Blue vector using Novagen PerfectlyPerBlunt CloningitKit. The cloned sequence was sequenced and confirmed to be the thiA gene of Clostridium acetobutylicum ATCC (824) strain. The plasmid thus obtained was designated as pT7Blue-CAC2873.

<Production of pCDFDuet-thiA>
An expression vector for expressing the thiA gene in E. coli was constructed as follows. First, PCR was performed using the following primers.

acat-NdeI-F: 5'-AAA CAT ATG AAA GAA GTT GTA ATA GC-3 '(SEQ ID NO: 40)
acat-XhoI-R: 5'-AAA CTC GAG CTA GCA CTT TTC TAG CAA T-3 '(SEQ ID NO: 41)
PT7Blue-CAC2873 prepared above was used as a template in PCR. The pair of primers was 10 pmol. The composition of the reaction solution was a 50 μl solution containing 12.5 nmol of dNTP and 1 μl of Pfu Ultra ^™ II fusion HS DNA polymerase (Stratagene) in 1 × Pfu Ultra ^™ II reaction buffer (Stratagene). The PCR thermal cycle was performed at 95 ° C for 2 minutes, followed by 5 cycles of 95 ° C for 20 seconds, 43 ° C for 20 seconds and 72 ° C for 40 seconds, followed by 95 ° C for 20 seconds, 50 ° C. 30 cycles of 20 seconds at 72 ° C. and 40 seconds at 72 ° C. were performed, followed by 3 minutes at 72 ° C. After the reaction, the stock was stored at 4 ° C.

The approximately 1.2 bp DNA fragment amplified by PCR was purified with MinElute® PCR® Purification® Kit and cloned into the pCR-Blunt® II-Topo vector using Zero® Blunt® TOPO® PCR® Cloning® Kit kit. The obtained vector was designated as pCR-Blunt II-TOPO-thiA. pCR-Blunt II-TOPO-thiA was cleaved with NdeI and XhoI, and a DNA fragment of about 1.2 Kbp was purified by agarose gel electrophoresis and inserted into the NdeI-XhoI site of pCDF-Duet (Novagen). The obtained plasmid was designated as pCDFDuet-thiA.

<Preparation of pCDFDuet-orfN>
An acetoacetyl-CoA synthase gene derived from Clostridium acetobutylicum and synthesizing acetoacetyl-CoA from malonyl-CoA and acetyl-CoA was cloned as follows. First, PCR was performed using the following primers.

OrfN-NdeI-F: 5'-AAA CAT ATG ACC GAC GTC CGA TTC CGC AT 3 '(SEQ ID NO: 42)
OrfN-XhoI-R: 5'-AAA CTC GAG TTA CCA CTC GAT CAG GGC GA 3 '(SEQ ID NO: 43)
In PCR, 20 ng of pHISORFn was used as a template. The pHISORFn described in JP 2008-61506 A was used. The pair of primers was 15 pmol. The composition of the reaction solution was a 50 μl solution containing 10 nmol dNTP and 0.5 μl PrimeSTAR HS DNA Polymerase (Takara Bio) in 1 × PrimeSTAR GC Buffer (Mg ²⁺ plus) (Takara Bio). The thermal cycle of PCR is 94 ° C for 1 minute followed by 5 cycles of 98 ° C for 10 seconds, 53 ° C for 5 seconds and 72 ° C for 1 minute, then 98 ° C for 10 seconds at 60 ° C. 30 cycles of 5 seconds at 72 ° C for 1 minute were performed, followed by 5 minutes at 72 ° C. After the reaction, the stock was stored at 4 ° C.

The approximately 1 Kbp DNA fragment amplified by PCR was purified with MinElute® PCR® Purification® Kit and cloned into the pCR-Blunt® II-Topo vector using the Zero® Blunt® TOPO® PCR® Cloning® Kit kit. The obtained vector was designated as pCR-Blunt II-TOPO-orfN. pCR-Blunt II-TOPO-orfN was cleaved with NdeI and XhoI, and a DNA fragment of about 1 Kbp was purified by agarose gel electrophoresis and inserted into the NdeI-XhoI site of pCDF-Duet (Novagen). The obtained plasmid was designated as pCDFDuet-orfN.

<Construction of pETDuet-ctfAB>
The ctfA and ctfB genes, which are acetoacetyl-CoA transferase genes derived from Clostridium acetobutylicum, were cloned. First, PCR shown below was performed using the genomic DNA prepared as described above as a template. In PCR, PfuUltra II fusion HS DNA polymerase (manufactured by STRATAGEN) and the following primers (underlined portions are restriction enzyme sites) were used.

ctfAB-NdeI-F: 5'-ATT CAT ATG AAC TCT AAA ATA ATT AGA TTT GAA AAT TTA AGG TC-3 '(SEQ ID NO: 44)
ctfAB-NdeI-R: 5'-AGA CTC GAG CTA AAC AGC CAT GGG TCT AAG-3 '(SEQ ID NO: 45)
The composition of the reaction solution in PCR was as follows.

The PCR thermal cycle was performed at 95 ° C for 2 minutes, followed by 30 cycles of 95 ° C for 30 seconds, 54.8 ° C for 30 seconds and 72 ° C for 2 minutes, and then 72 ° C for 7 minutes. After the reaction, the stock was stored at 4 ° C.

PCR (manufactured by Eppendruf) was performed under the above conditions, and a 1324 bp fragment was excised by 0.8% agarose gel electrophoresis. The fragment excised using QIAquickquiGel Extraction Kit (manufactured by QIAGEN) was purified and digested with NdeI and XhoI. Further, after purification with QIAquick PCR-Purification Kit (QIAGEN), it was inserted into the NdeI and XhoI sites of pETDuet-1 (Merck). The obtained sequence was sequenced to confirm that the intended plasmid was prepared. The plasmid thus obtained was named pETDuet-ctfAB.

<Construction of pETDuet-ADC>
The adc gene, an acetoacetate decarboxylase gene derived from Clostridium acetobutylicum, was cloned. First, PCR shown below was performed using the genomic DNA prepared as described above as a template. In PCR, PfuUltra II fusion HS DNA polymerase (manufactured by STRATAGEN) and the following primers (underlined portions are restriction enzyme sites) were used.

adc-SalI-F: 5'-CAC GTC GAC AAG GAG ATA TAA TGT TAA AGG ATG AAG TAA TTA AAC A-3 '(SEQ ID NO: 46)
adc-NotI-R: 5'-CAC GCG GCC GC T TAC TTA AGA TAA TCA TAT ATA ACT TCA GC-3 '(SEQ ID NO: 47)
The composition of the reaction solution in PCR was as follows.

The PCR thermal cycle was performed at 95 ° C for 2 minutes, followed by 30 cycles of 95 ° C for 20 seconds, 54.8 ° C for 20 seconds, and 72 ° C for 3 minutes, followed by 72 ° C for 3 minutes. In addition, after the reaction was completed, it was stocked at 13 ° C.

PCR (manufactured by Eppendruf) was performed under the above conditions, and a 735 bp fragment was excised by 1% agarose gel electrophoresis. The fragment excised using QIAquickquiGel Extraction Kit (manufactured by QIAGEN) was purified and digested with SalI and NotI. Furthermore, after purification with QIAquick PCR-Purification Kit (QIAGEN), it was inserted into the SalI and NotI sites of pETDuet-1 (Merck). The obtained sequence was sequenced to confirm that the intended plasmid was prepared. The plasmid thus obtained was named pETDuet-ADC.

<Construction of pETDuet-ADC-ctfAB>
Expression vectors for expressing the ctfA gene, ctfB gene and adc gene in E. coli were constructed as follows. First, pETDuet-ADC prepared above was digested with SalI and NotI, a 753 bp fragment containing the adc gene was excised by 0.8% agarose gel electrophoresis, and purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN). Moreover, pETDuet-ctfAB produced above was digested with SalI and NotI, and the obtained 6677 bp was ligated with the fragment. The obtained vector was named pETDuet-ADC-ctfAB.

<Construction of pCOLADuet-PDH>
The pdh gene, an isopropanol dehydrogenase gene derived from Clostridium beijerinckii, was cloned. First, PCR shown below was performed using pCR2.1-iPDH prepared in Example 1 as a template. In PCR, PfuUltra II fusion HS DNA polymerase (manufactured by STRATAGEN) and the following primers (underlined portions are restriction enzyme sites) were used.

PDH-EcoRI-F: 5'-G GA ATT CC A TGA AAG GTT TCG CAA TGT T-3 '(SEQ ID NO: 48)
PDH-PstI-R: 5'- AA C TGC AG A ACC AAT GCA TTG GTT ACA AAA TGA CTA CGG -3 '(SEQ ID NO: 49)
The composition of the reaction solution in PCR was as follows.

The PCR thermal cycle was performed at 95 ° C for 2 minutes, followed by 30 cycles of 95 ° C for 30 seconds, 50 ° C for 30 seconds and 72 ° C for 2 minutes, and then 72 ° C for 7 minutes. After the reaction, the stock was stored at 4 ° C.

PCR (manufactured by Eppendruf) was performed under the above conditions, and a 1056 bp fragment was excised by 0.8% agarose gel electrophoresis. The fragment excised using MiniEluteElGel Extraction Kit (manufactured by QIAGEN) was purified and digested with EcoRI and PstI. After purification with QIAquick PCR-Purification Kit (QIAGEN), it was inserted into the EcoRI and PstI sites of pCOLADuet-1 (Merck). The obtained sequence was sequenced to confirm that the intended plasmid was prepared. The plasmid thus obtained was named pCOLADuet-PDH.

<Recombinant E. coli production>
The pCDFDuet-thiA, pCDFDuet-orfN, pETDuet-ADC-ctfAB, and pCOLADuet-PDH prepared above are classified into E. coli BL21 (DE3) E. coli K strains manufactured by Takara Bio Inc. in the combinations of A to F shown in Table 5 below. E. coli NovaBlue (DE3) was transformed. Recombinant E. coli transformed with the combination of the expression vectors A to F into E. coli BL21 (DE3) was named A / BL21, B / BL21, C / BL21, D / BL21, E / BL21 and F / BL21, respectively. Recombinant E. coli obtained by transforming the combination of the expression vectors A to F into E. coli NovaBlue (DE3) was named A / NB, B / NB, C / NB, D / NB, E / NB, and F / NB, respectively.

When culturing the obtained recombinant Escherichia coli, first, a trace element having the following composition was prepared.

In addition, SD-7 medium was prepared as follows. NH ₄ Cl 7.0 g, KH ₂ PO ₄ 1.5 g, Na ₂ HPO ₄ 1.5 g, K ₂ SO ₄ 0.35 g, MgSO ₄ 7H ₂ O 0.17 g, Difco Yeast Extract 5.0 g, Trace Element 0.8 ml 0.8 After dissolving in L deionized water, the pH was adjusted to 7.0 with 5M NH ₄ OH. The whole volume was made up to 1 L with deionized water and autoclaved.

Further, SD-8 medium was prepared as follows. NH ₄ Cl 7.0 g, KH ₂ PO ₄ 7.5 g, Na ₂ HPO ₄ 7.5 g, K ₂ SO ₄ 0.85 g, MgSO ₄ 7H ₂ O 0.17 g, Difco yeast extract 10.0 g, 1 L of trace element 0.8 ml Was dissolved in deionized water and autoclaved.

Furthermore, when each recombinant E. coli described above was cultured in SD-7 medium or SD-8 medium, antibiotics shown in the following table were added as necessary. In the table, Amp: ampicillin, Km: kanamycin (manufactured by SIGMA), Str: streptomycin and Tet: tetracycline.

For each of the obtained recombinant Escherichia coli, a single colony was inoculated into 5 ml of SD-7 medium containing 2% final glucose (manufactured by Wako Pure Chemical Industries, Ltd.) and cultured overnight at 37 ° C. Next, 50 ml of SD-8 medium containing glucose having a final concentration of 2% was placed in a 500 ml baffled Erlenmeyer flask, 500 μl of an overnight culture was inoculated, and cultured at 37 ° C. and 130 rpm. When O.D600 was 1.0 or less, IPTG having a final concentration of 0.1 mM was added, and the culture was further continued. After addition of IPTG, 0, 3, 6, 9, 24, and 30 hours later, 5 ml of the culture solution was dispensed into a test tube with a screw cap and stored at −30 ° C. (partially, also after 48 hours). Glucose was additionally added so that the final concentration was 2% 24 hours after the addition of IPTG.

Thereafter, the culture solution stored frozen at −30 ° C. was thawed at room temperature. After stirring well with Vortex, 1 ml of the culture solution was put into an Eppendorf tube that had been weighed in advance, and centrifuged at 13000 rpm for 10 minutes at 4 ° C. using a cooling small centrifuge (manufactured by TOMY). The Eppendorf tube from which the supernatant was removed was dried at a temperature of Low for about 4 hours using Speed Vac (manufactured by SAVANT). Thereafter, the weight of the Eppendorf tube was measured, and the value obtained by subtracting the weight measured in advance was taken as the dry cell weight.

The test tube with screw cap containing the remaining culture solution (4 ml) is centrifuged at 1000 g for 5 minutes at room temperature using a desktop multi-centrifuge LC-230 (manufactured by TOMY). Separated into cells. 2 ml of the supernatant was placed in a 20 ml headspace crimp vial, capped and placed in a 60 ° C. warm bath for 15 minutes. Thereafter, component analysis was performed on isopropanol and the like by GC-MS / HSS.

GC-MS / HSS was an HP6890 / 5973/7694 GC-MS / HSS system (manufactured by Hewlett-Packard). The column used was J & W DB-624 (0.32 mm × 60 m, film thickness 1.8 μm), and the analysis conditions were as follows.

<GC-MS analysis conditions>
[Inlet parameters]
Inlet temperature: 260 ℃
Split ratio: 1/20
Carrier gas: Helium 1.0ml / min
[Oven heating conditions]
Heat at 40 ° C for 5 minutes
Heat to 75 ° C at 5 ° C / min
Heat to 260 ° C at 100 ° C / min
[Detector conditions]
Detector temperature: 260 ° C
<Head space sampler conditions>
[Zoom Temp]
Oven: 60 ℃
Loop: 150 ° C
Transfer Line: 200 ℃
[Event Time]
GC Cycle Time: 35 minutes
Vial EQ Time: 15 minutes
Pressuriz. Time: 0.5 minutes
Loop Fill Time: 0.2 minutes
Loop EQ Time: 0.2 minutes
Inject Time: 1.0 minute
[Vial Parameter]
Shake: HIGH
[Other]
Vial pressurization: 15psi
<Reference material>
Ethanol (specific gravity: 0.789)
Acetone (specific gravity: 0.789)
Isopropanol (specific gravity: 0.784)
Acetic acid (specific gravity: 1.05)
The above-mentioned standard substance was adjusted to an appropriate concentration, and the% concentration (V / V) was calculated from the calibration curve, and the weight concentration was calculated in consideration of the specific gravity. The production amounts of acetone and isopropanol of the recombinant Escherichia coli prepared in this reference example are summarized in the following table.

From this result, it can be seen that the recombinant Escherichia coli introduced with the pdh gene in addition to the ctfAB gene and the adc gene showed a decrease in acetone production and an increase in isopropanol production. It can also be seen that the production of isopropanol is dramatically improved in the recombinant Escherichia coli further introduced with the acetoacetyl CoA synthase gene compared to the recombinant Escherichia coli introduced with the ctfAB gene, adc gene and pdh gene. However, among the acetoacetyl-CoA synthase genes, the gene encoding an enzyme using malonyl-CoA and acetyl-CoA as a substrate is more isopropanol-producing than the gene encoding an enzyme using bimolecular acetyl-CoA synthesis as a substrate. It has been found that the effect of improving is low. On the other hand, in Example 1, it was shown that the use of an acetoacetyl-CoA synthetase gene encoding an enzyme having malonyl-CoA and acetyl-CoA as substrates can significantly improve isopropanol productivity. That is, it can be said that this result shown in Example 1 cannot be predicted from the knowledge obtained from recombinant Escherichia coli introduced with the acetoacetyl-CoA synthase gene and the isopropanol biosynthesis related gene group.

Claims (17)

1. It is characterized by culturing a recombinant yeast introduced with an acetoacetyl CoA synthase gene and an isopropanol biosynthesis related gene group related to a metabolic pathway for synthesizing isopropanol from acetoacetyl CoA, and obtaining isopropanol from the culture A method for producing isopropanol.
2. The method for producing isopropanol according to claim 1, wherein the acetoacetyl-CoA synthetase gene encodes an enzyme that catalyzes a reaction for converting acetyl-CoA and malonyl-CoA into acetoacetyl-CoA.
3. The method for producing isopropanol according to claim 2, wherein the acetoacetyl-CoA synthase gene is a gene derived from a microorganism of the genus Streptomyces (ORFn gene).
4. The acetoacetyl-CoA synthase gene encodes a protein having the amino acid sequence set forth in SEQ ID NO: 1, or has an amino acid sequence having 80% or more coincidence with the amino acid sequence of SEQ ID NO: 1, The method for producing isopropanol according to claim 2, which encodes a protein having a function of synthesizing acetoacetyl-CoA from acetyl-CoA.
5. The isopropanol biosynthesis related gene group is a gene selected from the group consisting of an acetoacetyl CoA transferase gene, an acetoacetate decarboxylase gene, and an isopropanol dehydrogenase gene. 2. The method for producing isopropanol according to claim 1, wherein a gene that does not exist in the gene group is introduced.
6. 6. The method for producing isopropanol according to claim 5, wherein the acetoacetyl CoA transferase gene is a ctfA gene and a ctfB gene derived from Clostridium acetobutylicum.
7. The method for producing isopropanol according to claim 5 or 6, wherein the acetoacetic acid decarboxylase gene is an adc gene derived from Clostridium acetobutylicum.
8. The method for producing isopropanol according to any one of claims 5 to 7, wherein the isopropanol dehydrogenase gene is a pdh gene derived from Clostridium beijerinckii.
9. The method for producing isopropanol according to claim 1, wherein the acetoacetyl-CoA synthase gene and the isopropanol biosynthesis related gene group are introduced into the genome of yeast as a host.
10. A recombinant yeast into which an acetoacetyl CoA synthase gene and an isopropanol biosynthesis related gene group related to a metabolic pathway for synthesizing isopropanol from acetoacetyl CoA are introduced.
11. 11. The recombinant yeast according to claim 10, wherein the acetoacetyl-CoA synthetase gene encodes an enzyme that catalyzes a reaction for converting acetyl-CoA and malonyl-CoA into acetoacetyl-CoA.
12. The recombinant yeast according to claim 11, wherein the acetoacetyl-CoA synthase gene is an acetoacetyl-CoA synthase gene (ORFn gene) derived from a microorganism belonging to the genus Streptomyces.
13. The acetoacetyl-CoA synthase gene encodes a protein having the amino acid sequence set forth in SEQ ID NO: 1, or has an amino acid sequence having 80% or more coincidence with the amino acid sequence of SEQ ID NO: 1, The recombinant yeast according to claim 11, which encodes a protein having a function of synthesizing acetoacetyl-CoA from acetyl-CoA.
14. The isopropanol biosynthesis related gene group is a gene selected from the group consisting of an acetoacetyl CoA transferase gene, an acetoacetate decarboxylase gene and an isopropanol dehydrogenase gene, and among the genes of these isopropanol biosynthesis related gene groups The recombinant yeast according to claim 11, wherein a non-internal gene is introduced.
15. The recombinant yeast according to claim 14, wherein the acetoacetyl-CoA transferase gene is a ctfA gene and a ctfB gene derived from Clostridium acetobutylicum.
16. The recombinant yeast according to claim 14 or 15, wherein the acetoacetic acid decarboxylase gene is an adc gene derived from Clostridium acetobutylicum.
17. The recombinant yeast according to any one of claims 14 to 16, wherein the isopropanol dehydrogenase gene is a pdh gene derived from Clostridium beijerinckii.

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